Also, echo out your data to see what it actually contains -
PHP Code:
echo "<pre>";
print_r($_POST);
echo "</pre>";
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Error checking, error reporting, and error recovery. If your code does not have these to get it to tell you why it is not working, what makes you think someone in a programming forum will be able to tell you why it is not working???
I've encountered this problem before, it was IE on windows that was causing the problem as I think it was passing a X, Y post variable instead of the submit parameter. The work around was to add a hidden form field and listen for that.
In the form add a hidden field of 'action' with the value of 'add'
This actually probably only happens to be a problem in firefox or IE. I've noticed that when you use type="image" it tends to mess things up. What I do is use css to fix the problem.